Fiber-reinforced composite materials comprising a reinforcing fiber and a thermosetting resin enjoy good balance between lightness and mechanical properties, and they have been widely used as structural members of an aircraft, automobile, or ship, housing of electronic device, sports applications, building materials, and other industrial materials. With increase of such demands, improvement of the production cycle has been a major technical challenge for the fiber-reinforced composite materials. One means for improving the production cycle is use of a release film in the molding by applying heat and pressure which is an improvement in the step of demolding the fiber-reinforced composite material from the mold.
Patent Document 1 discloses a release film having an excellent releasability from thermosetting resin members such as epoxy resin board.
Patent Document 2 discloses a method for producing a single-sided board wherein a prepreg is laminated with the release film.
Patent Document 3 discloses a release film used in the flexible printed board.
Patent Document 4 discloses a release film wherein a grain pattern is formed on the surface of the molded article by the transfer of the pattern of the weaven reinforcing fibers in the prepreg in the press molding.
However, the fiber-reinforced composite materials disclosed in Patent Documents 1 to 3 are those having plate shape, and Patent Document 4 relates to patterns on the surface of the fiber-reinforced composite material. With increasing demands on the fiber-reinforced composite materials, the fiber-reinforced composite materials are expected to have formability into various shapes in addition to improvements in the production cycle as described above, and in these applications, however, the fiber-reinforced composite materials according to the inventions disclosed in the Patent Documents 1 to 4 sometimes suffered from poor appearance.